Inhibiting corrosion with chromiumquaternary ammonium salt compositions



iteta This invention relates to a new method for inhibiting corrosion inindustrial process Water systems. More specifically, it relates tonon-corrosive aqueous liquids which contain minor amounts of corrosioninhibiting chemicals.

In under Water systems in which water moves through such units ascondensers, engine jackets, cooling towers and the like, corrosion isfrequently quite severe due to the fact that water is concentratedseveral times during the course of the various processes. Such systemswhich are for the most part, recirculating types, contain equipmentwhich uses as its structural material such metals as iron and steel,brass, copper, admiralty metal as well as minor amounts of zinc andother non-ferrous metals.

One of the best inhibitors for rendering such systems non-corrosive arethe well known alkali metal chromates. While chromates are economicaland give good results, in many cases it has frequently been theexperience of the art that pitting and tuberculation of the.varioussurfaces occurs when chromates are used alone. The problem of pittingand tuberculation which sometimes occurs with chromate inhibitors may bemitigated using chromates in conjunction with phosphates. Although suchcombinations of inhibitors have proven to be of value in protectingindustrial process water systems, they are not entirely satisfactoryfrom all standpoints.

Many attempts have been made to develop new inhibitors for aqueoussystems of the type described above, with much effort being directedtowards discovering an organic inhibitor of the so-called film formingtype. Materials such as amine compounds, quaternary ammonium salts, andcertain carboxylic acids which are known to be efiective inhibitors formany types of systems have failed to protect industrial process watersystems at low economical dosages.

It would be a valuable contribution to the art if an inhibitorcontaining an organic film forming component could be devised forindustrial process systems which would be effective at low economicaldosages and would be successful in preventing tuberculation and pittingof metals in contact with such systems.

It has been discovered that extremely'valuable corrosion protection tometals in contact with industrial process waters may be afforded bytreating such systems with a combination treatment which comprises awater soluble hexavalent chromium compound in conjunction with aspecific type of water dispersible quaternary ammonium salt. In apreferred embodiment, the water soluble hexavalent chromium compoundsand the water dispersible quaternary ammonium salts are advantageouslycombined with minor amounts of certain compounds capable of producing inaqueous solution a heavy metal cation such as zinc, cobalt, nickel,mercury and trivalent chromium cations.

The various compositions described above as the inhibitors of theinvention are preferably used at certain I amazze Patented Feb. 26,l2$63 dosage levels in the Water to provide optimum results. In the caseof the hexavalent chromium compounds, the dosage is maintained atbetween 10 and 200 parts per million (expressed as CrO Preferably thedosage is maintained between 15 and 50 parts per million. The quaternaryammonium salt is maintained in the Water at a dosage level ranging atgenerally between 0.5 to 10 parts per million and preferably between 2and 6 parts per million. In the case of the heavy metal compounds, thedosage is maintained at between 0.25 and 10 parts per million with thepreferred range being at 2 to 6 parts per million. These latter dosagesare expressed in terms of the metal rather than the total compound withwhich it is associated.

In order to achieve optimum results, it is beneficial that the pH of thewater be maintained within certain specific ranges. As a general rule,these ranges may vary between 5.5 and 8.5, although the best results areachieved when the pH is kept within the ranges of 6.5 to 7.5.

The hexavalent compounds of chromium are most suitably chosen from thealkali metal chromates and dichromates such as sodium dichromatedihydrate, sodium chromate (anhydrous), sodium chromate tetrahydrate,sodium chromate hexahydrate, sodium chromate decahydrate, potassiumdichromate, potassium chromate, and the like.

The quaternary ammonium salts used in the practice of the invention maybe selected from a large group of known and commercially availablematerials. It is essential to the practice of the invention that theparticular quaternary ammonium salt must contain at least 8 carbon atomsand preferably at least one acyclic organicradical of at least 12 carbonatoms in chain length. The higher acyclic organic radical may contain asmany as 22 carbon atoms. Preferably the higher acyclic organic radicalshould be from 16 to 18 carbon atoms in chain length. A preferred groupof quaternary ammonium salts are the quaternary ammonium chlorideshaving the following general structural formulae:

where R is a higher aliphatic group of from 16-18 carbon atoms in chainlength, e.g., hexadecyl, heptadecenyl, octadecyl, and octadecenyl, and RR and R are lower aliphatic carbon groups of from 1-6 carbon atoms inchain length, e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl,amyl, isoamyl, and hexyl. Another useful group of quaternary ammoniumsalts are the higher aliphatic substituted imidazolinium salts.

For purposes of illustrating several quaternary ammonium salts of thetype which may be used in the practice of the invention, Table I ispresented. Also included in this table are certain amines which areconsidered inoperative.

TABLE I Quaternary Ammonium Salts A. lmidazolinium salts:

(l) Z-methyl-l-(Z hydroxy ethyl) 1 benzyl imidazolinium chloride (2)2-coco-l-(2-hydroxyethyl) -1-benzyl imidazolinium chloride (3)2-coco-l-(hydroxyethyD-l (4 chlorobutyl imidazolinium chloride 3 l (4)2-coco-1-(2-hydroxyethyl)- 1 octadecenyl imidazolinium chloride (5)2-tall oil fatty-1-(2-hydroxyethyl)-l-benzyl imidazolinium chloride 1(6) 2-tall oil fatty-I-(Z-hydroxyethyl)-1-(4-chlorobutyl) imidazoliniumchloride 1 (7 2-heptadeccnyl-1- (Z-hydroxyethyl) -1- l-chlorobutyl)irnidazolinum chloride (8) Z-heptadecenyl-1-(2-hydroxyethyD-l-benzylimidazolinium chloride (9) Z-heptadecyl-l-(hydroxyethyD-l .octadecylimid azolinium ethyl sulfate i B. Aliphatic quaternariesi (10) Dodecyltrimethyl ammonium chloride: (ll) Hexadecyl trimethyl ammonium chloride(12.) Octadecyl trimethyl ammonium chloride (.13) Coco trimethylammoniumchloride 14) Soyatrimethyl ammonium chloride (15) Tallow trimethylammonium chloride l6) Dicoco dimethylammonium chloride 17.) Cocoamine Rx15 moles EtO quaternized with methy h o e (18) Octadecyl amine Rx 2moles EtQ quaternized withmethyl chloride (19;),Oetadecenyl amine R2; 2moles EtQ quaternized withmethyl-chloride (19A,) D v r s atsd. l l d m yo nium chloride C. Amines;

(-20) Soyaamine- (:21 Hydrogenated tallowamine (2 ,Coco amine 1),Miscellaneous quaternary ammonium compounds:

' (23) Lauryl isoquinolini-um bromide. (24) Cetyl isoquinolinium bromide(25)" Lauryliisoqinolinium chloride (26 Alkyl (C H to C t-Idimethyl3,4,-dichlorobenzyl ammonium chloride and alkenyl- (C to C-)-'.dimethyl ethyl; ammonium bromides injtbe ratio 5:1 (27)OctadecenyI-Q'dimethyl benzylammonium chloride (28) l dodecyl-izrbenzylpyridinium bromide (29*). l-methyl-Lethyl piperidinium bromide (30:)Hexadecyl pyridinium bromide. (31) N.-soya-N'ethyl morpholiniumethosulfate [From the above table it will be seen that the quaternaryammonium salt may have a wide variety of substituents just so long astheycontain a higher alkphatic group of the type previously specified.Other useful imidazolinium salts which meet the specifications set forthherein are disclosed in Rydell, US. 2,733,325. The preferred quarternaryammoniumsaltshave only one higher saturated or unsaturated aliphaticgroup 'of at least 12 carbon atoms since they are most readilydispersible in the aque O'us systems in which they are employed. Thehigher aliphatic radicals may be mixed, as, for. example, those radicalsderived from vegetable oils and animal fats. The expression dispersiblewhen referring to thequa ternary ammonium salts is meant to refer tothosematerials that are either water soluble or thosethat may becolloidally dispersed in aqueous. systems at use concentrations.

' The heavy metal cations are derived from their water soluble salts orbases. Examples of typical compounds that fall within this category arethe following: zinc sulfate, cobaltous'chloride, nickel iodide, mercuricacetate, chromic chloride, zinc chloride, cobaltous sulfate, andmercurous chloride.

When making concentrated solutions for the purpose of feeding, itisfrequently desirable to use the acidic salts of the heavy'metalmaterials such as, for instance, zinc sulfate and also to use an acid oran acidic material Essentially free from rosin acidcornponents.

such as sodium hydrogen sulfate or sulfamic acid whereby the pH of theresulting concentrated solution is adjusted between 3.5 and 5.

In using the inhibitors described above, it is helpful if the hexavalentchromium compounds and the heavy metal ionizable compound is combinedinto one formulation. The quaternary ammonium salt is used as a separateentity, since experience has shown that combining all the ingredientsinto a unitary product causes a reaction to occur between the chromateand the quaternary ammonium salt, which reaction forms an insolublematerial. When fed separately to industrial process water systems at thedosages previously specified, no such insoluble reaction products areformed. Typical products The polyphos-phate in Formula A is. added forthe purpose of stabilizing the calcium carbonate which may be present inthe water. If calcium carbonate does. not present a problem in the waterto be treated, the polyphosphateis omitted. However, since this. processdoes not adversely affect the usefulness of the treatments, it isdesirable to use it in most cases. The phosphate may be used in dosagesof .5 to 2 parts per million, although dosages as high as l to 9 par-tsper million may also be used, butgenerally the dosage need never-exceedl part per million. It should be noted that at these dosage levels the"phosphate neither adds-nor detracts from the inhibiting properties ofthe compositions described abo-ve.

EVALUATION OF THE INVENTION T he. test methods used to determine theefiicacy of the inventionwhen used to inhibit the corrosion ofindustrial process waters are of three. types. These test methods are.describedbelow in detail under the headings of test methods A, B, andC.

Test method A.The specimensused are weighed, sandblasted mild steelcoupons (SAE 1010) 1 inch wide by 2 inches long by 20 gauge. 500 ml. ofthe test water was used. The treatment was added (generally from astocksolution) and the pH adjusted to 6.5 with sulfuric acid or sodiumhydroxide. The test water was prepared to simulate a typical coolingwater. This synthetic water had the following composition:

-P-m- Total hardness (as CaC O 400 Calcium hardness (as CaCO 250Magnesium' hardness (as CaCO 150 Total alkalinity (as CaCO 5 Sulfate (asNa SOQ 1400 Chloride (as NaCl)' SOQ The test coupon was immersed and thesolution stirred at 1750 rpm. with a bell shaped stirrer for 24 hours.At the end of this time the coupon was removed from the water and airdried. The coupon was then examined and scored according to the weightloss of the coupon and visual evaluation of factors such as pitting anddeposit. The test was run at F.

Test method B.Thesecond laboratory testing procedure Was alsoquantitative in nature and involved measurement of corrosion rates ofmetallic coupons. These were subjected to certain specific sets oftestconditions designedjto. approximate those found in. field operationwhich contribute to the corrosion. While it was obviously necessary tomake some adjustments for small scale laboratory testing, a strongeffort was made to incorporate those variables which are the majorfactors in causing corrosion in heat exchangers associated with coolingtower systems. The principal corrosive factors operating on the couponsare:

High dissolved oxygen level High chlorides, sulfates and total dissolvedsolids Low alkalinity, low pH (66.5

This test combined the advantages of both the batch type test and theonce through test and was essentially an intermittent, once-throughtest. With this system, conditions were maintained constant throughoutthe test while a relatively small volume of water was used.

The equipment consisted of a series of individual units. Each unit wascomplete and independent of the others. It consisted of a five-gallonbottle which formed the reservoir for the test water. The water flowedfrom the reservoir by gravity to a feed assembly that controlled thehead level. From there the water passed through a solenoid valve thatwas activated by an electrical timer. The timer opened the valve everyeighteen minutes to allow 40 ml. of the water to flow into the testvessel that was partially immersed in a constant-temperature oil bath at140 F. The rate of ilow was about 3.2 liters per day, corresponding to a1.3 fold replacement of the water daily. The water left the test vesselthrough an overflow tube. The standard water used in this test had thesame composition as the one used in Test Method A. Variations covering arange of typical cooling waters have been checked with results similarto those described here.

The test specimens were made of No. gauge SAE 1010 mild steel, and wereone inch wide and 2 inches long. They were suspended in the test vesselfrom a inch hole drilled /4 inch for the short edge. The panels wereprepared by sandblasting with flint shot sand. After sandblasting theywere cleaned first in toluene and then in acetone, and weighed andplaced in the test vessel. After the test they were removed and thencleaned by a second immersion in muriatic acid inhibited withformaldehyde. They were then removed from the acid and neutralized in asoda ash solution. The panels were then rinsed in water, dipped inacetone and air dried. Test panels were stored in a heated cabinet at105 F. before weighing.

The test vessel was a Pyrex jar 6 inches in diameter and 8 inches tall,with an overflow tube at a point two inches from the top. The vessel wascovered by a stainless steel lid that had a hole in the center toaccommodate the stirrer, and holes around the edge for mounting theglass hook holders. The stirrer had a 1 inch by 2 inches paddle androtated at 175 r.p.m. There were also holes in the lid to admit the tubefrom the reservoir, and an aerator. The tests were aerated continuously.These tests can be run for any length of time desired. Six coupons canbe mounted in each test vessel. One was removed periodically todetermine if the corrosion rates had leveled off. During the first fewdays of a test run the corrosion rates were relatively high and tendedto be less reproducible, and for this reason it was necessary to run thetest from 1530 days. The initial corrosion rate for the system with noinhibitor present was about 80 m.p.y. After an exposure of 15 days, therate will reach equilibrium at about m.p.y.

Test method C.These tests were designed as a modification of test methodB, and have a heat transfer surface which would act as a specimen forevaluation of corrosion and fouling. The test unit had a reservoir, feedsystem, and test vessel identical to those of test method B, except thatno oil bath was used. Solution was pumped from the vessel by means of acentrifugal pump, then vertically through the annular space between a 17inch long, /2 inch out diameter (O.D.), 16 gauge tube, and

cc./sec. 10- NRe Velocity (ft/sec.)

The coding water flow to the jacket was controlled by means of athermostat in the test vessel, so that the vessel could be maintained atany desired temperature which, in these tests, was either or 160 F.

Using test method A, several of the quaternary ammonium salts in Table Iwere tested alone and in combination with sodium dichromate to determinetheir eifectiveness. These reuslts are presented below in Table II. Theresults were expressed in terms of P, F or G with the P indicating thatthe test material showed little or no activity, P meaning that it showedmoderate activity, and G meaning that the material was good under thetest conditions.

TABLE II Evaluation Test No. Description of test material Alone 1 CrO4additive 2 2 heptadecenyl 1 (2 hvdroxethyD- 1 (4 chlorobutyl)imidazolinium chloride.

2 heptadecyl 1 (2 hydroxyethyD- l-benzyl imidazolinium chloride.

2 heptadecyl 1 (hydroxyethyl) 1- octadecyl imidazolinium ethyl sulfate.

Dodecyl trimethyl ammonium chlo- Hexadecyl trimethyl ammonium chlo-Octgdecyl trimethyl ammonium chlo- Coco trimeth vl ammonium chloride..Soya trimethyl ammonium chloride Tallow trimethyl ammonium chlorideDicoco dimethyl ammonium chloride Coco amine Rx 15 moles EtO quaternizcdwith methyl chloride. Octadecyl amine Rx 2 moles EtO quaternized withmethyl chloride. Octadccenyl amine Rx 2 moles EtO qunternized withmethyl chloride. Dihvdrogenated tallow d'unethyl ammonium chloride.

e e e e -s c e e e *1 *e Q Q QQQQ Q Q n 1 Using steel coupons, testmaterial (200 ppm.) was evaluated as a corrosion inhibitor; pH 6.0-7.0;temperature F.

2 Using steel coupons, test material (40 ppm.) was evaluated as anadditive to sodium dichromate- (40 ppm. Cr04) to reduce corrosion andpitting; pH 6.0-7.0; temperature 140 F.

I Free from rosin acid components.

To further evaluate the invention, test method B was employed. The testswere designed to determine more critically conditions favoring the useof various ingredients. The treatment and test results are given inTable 111.

TABLE 11 1- Evaluation of Chromate,-,Zinc Quaternqry TreqtmentsTREATMENT Gontinual, first week Remainder of run Quartemary in Analysis,p.p.m. in vessel, days .Composlreservoir (5 days) 7 Test tion N o. 7 N03#0111 74 Table]; (304, Zn, Quat, 0x04, Zn, Quat, Theor. Actual 1 8 22 2Sp,p,m. p.p.m. p.p.m. p.p.m. p.p.m. p.p.m.

1 A. Effect of Quat Concentration B. Effect of Zinc Ooncentrat-ion 12 7so 2 so 2 2 2 12 I 30 4 2 30' 4 2 I 2 12 30 3 30 6 3 3 2.8 2.5 0.7 0.4.1.0

'C. Efleet of Initial Chromate Slug in Vessel 12. 20 2 2o 4 2 2 2.0 2.41.9 0.6 1.0 12' 20 4 2 20 4 3 8 1. Q 1. 3 1. 6 0. 6 (1,9 12 20 2 20 2 2z 1. 5. 0.9 1. 0' 0. 9'

' "DI Efie'ct'of Treatment Level E. Comparison on Active Dosage Basis 1230 2 30 2 2 2. 0 I 1.0 1. 1 0.7 0. 8 19A 30 4 2 30 4 2 2 1. 9 4'. 2 0.8O. 8 0.4 '8 30 2 30 4 2 2 0.5 1. 3 0. 1 O. 3 0.6

" F. Test without Quartemary 17 Blank 30 2 30 2 OBSERVATIONS AND RESULTSTubemulation-pittlng evaluaiionfi days Overall film Cumulativecorrosion, weight loss, mgs. Test formation Overall eon. 3. 7 rate,m.p.y.

1 s I 2 28 1 22 2s A. Effect of QuaLConcentration B. Efiect of ZincConcentration 0. Effect of Initial Chromate Slug in Vessel D. Efieot ofTreatment Level' E. Comparison on Active Dosage Basis F. Test withoutQiiarternry "21241251 result.

employed in order to determine more completely the benefits of theinhibitors. These results are presented in 16 sorption was only a smallfraction of the rate of loss by normal blowdown. Thus, the loss ofquaternary to the wood in a cooling tower would be a factor during theini- Table IV. tial treatment but this is counteracted by increasing theTABLE IV Evaluation of Chromate-Zinc-Quaternary Treatments Obtained WithHeat Transfer Apparatus Pretreatment Follow-up treatment Observations ontube Quat. slug Quaternary (Table I) Test Type cnc., 01-0 Zn, period,Film Grease Tuberoulap.p.m. p.p.m. p.p.m. days formation removal tionType p.p.m.

A. Blank none 40 4 14 Heavy.

B. Comparison of Quats on a Cost-Dosage Basis Quat Slug 40 30 6 3.0 8Quat Slug 40 3O 6 19A 3. 9 8 Quat Slug 40 30 6 8 6.0 8

0. Effect of Initial Quat Concentration Quat Slug 40 30 6 12 5.0 Slight.Quat Slu 6O 3O 6 12 5.0 Do. Quat Slug SO 30 G 12 5. O Do. Quat Slug 603O 6 12 3.0 Mod. High Quat 60 2O 4 12 2.0 Trace Pretreatment Quaternaryin Deposit analysis, mg. Weight data vessel, p.p.m.

Sca1e+ Quat. slug corr. Corr. Type c0110., 3 day 8 day PO; 0a Fe ORQuet. Zn prod.+ loss p.p.m. film,

A. Blank none 54 155 503 299 B Comparison of Quats on a Cost'DosageBasis Quat Slug 40 1. 2 2. 3 22 203 8G Quat Slug 40 3. 3 4. 11 243 132Quat Slug 40 2.1 1. 3 282 140 Quat Slug 96 16 0.2 2. 8 308 225 Quat Slug15 2. 5 15 157 S1 Quat Slug 16 3.1 7 174 85 Quat Slug 31 0. 3 6 $7 aHigh Quat 61 0 58 1 Composition 12 of Table I used for slug in the testvessel at start of test. 2 32 p.p.m. OrOs, 6 p.p.m. Zn and 60 p.p.m.Comp. 12 for 4 days at 125 F.

To further illustrate the industrial utility of the in vention, atypical quaternary ammonium compound, octadecyl trimethyl ammoniumchloride was tested to determine its rate of absorption on redwood, amaterial commonly used in cooling tower construction. The test methodmay be briefly described as follows:

Extracted redwood blocks were placed in contact with a volume of thequaternary ammonium salt solution such that the areazvolume ratio (34.5sq. in.:1000 ml.) complied with the conditions of a typical coolingtower. In these tests the initial concentrations of the material were20, 40, 80, and 120 p.p.m.; at intervals small samples (1% by volume)were Withdrawn for analysis. The results (Table V) show that initiallyroughly 20 p.p.m. of the quaternary ammonium salt is absorbed but thatthe rate drops off after a few hours. Although the salt continued to beabsorbed for the next three weeks, the rate of ablevel of the initialhigh quaternary treatment. The results of these tests are presented inTable V below.

TABLE V Absorption of Oczadecyl T rimethyl Ammonium ChlorideConcentration 01' compound found (p.p.m.) Time y 20 40 p.p.m. p.p.m.p.p.m. p.p.m

From Table II it will be observed that most of the quaternary ammoniumsalts tested were relatively inactive as inhibitors per se. Whencombined with the chromate, protection was afiforded.

An interesting result presented in Table III is the fact that when thesystem was initially treated, using a high dosage of quaternary ammoniumsalt, e.g., 40parts per million, and the lower concentration, viz.,parts per million was maintained, better protection wasatforded thanwhen the dosage of thev quaternary ammonium salt was held constantthroughout the test, The reason for this phenomenon is believed to bethat the initial high dosage. tends to form a protective coating on thesurface which is subsequently maintained by the lower steady dosage.

Also observed from the results shown in Table III is that 40 parts permillion of the quaternary ammonium salt, when maintained on a steadybasis, is unnecessary once the protective coating is formed. The dosagesfrom between 2 to 5 parts per million ofg the quaternary and frombetween 2 and 6 parts per million of the zinc salt give generallysatisfactory, results It becomes evident from the above tests that onemethod of practicing the invention: is to feed relatively high dos agesof the quaternary ammonium salts to the system to form an initialprotective film which is then subsequently maintained by the use oflower continual dosages. The amount of quaternary ammonium salt used toform this protective film, as well as the time in which it takesthe filmto be formed, will, of course, be dependent upon the environmentalfactors present in each system. Thus, for instance, pH, temperature,dissolved solids, and the types of metals present must be taken intoconsideration. As a general rule, however, itmay be stated that theprotective films may be morereadily formed. by using large dosages ofthe quaternary ammonium salts for short periods of time rather thanusing smaller dosages for long periods of time. In the case of a typicalcooling tower system at least 40 parts per millon of the quaternary forat least 3 days should be used for forming the protective film.

The pretreatment with higher dosage quaternary ammonium salts provides asimple andefiiective method for stopping initial corrosion rates whenindustrial systems are first put on stream. It-will be understood,however, that the invention does not require such a pretreatmentoperation since in most cases a continual feed of the chemical at loweconomical dosages will eventually form an effective protective filmthat will be self-maintaining.

As a further guide to forming aninitial protective. film of thequaternary ammonium salt, the pretreatment of the system should employfrom 20 to- 60 parts per millionand preferably 30 to 40 parts permillion of the quaternary salt for a period of time ranging from 7 hoursto 30 days. Quite frequentlyonly several days are required. Thepretreatment is conducted using the same amountof chromate andheavymetal as previously specified.

In the specification, EtO is an abbreviation for ethyl-. ene oxide.Thus, in Table II, a test material coco amine Rx moles EtO quaternized'with methyl chloriderefers to an aminederived from coconut oil which hasbeen oxyalkylated with 15 molesof ethylene oxide per mole of amine andthen reacted with one mole, of methylene chloride per mole of amine.

The invention is hereby claimed asfollows:

1. A non-corrosive industrial process water which comprises a majorportion of water, at least 10 parts per million of a water solublehexavalent compound of chromium, calculated as CrO and at least 0.5 partper million of a water dispersible quaternary ammonium salt whichcontains at least one acyclic organic radical having at least 8 carbonatoms, the pH of said. water being within the range of 5.5 to 8.5

2. A non-corrosive industrial process water which comprises a majorportion of water, 10 to 200 parts per million of a water solublehexavalent compound of chromium, calculated as CrO and 0.5 to 10 partsper million 12 of a water dispersible quaternary ammonium salt which hasat least one acyclic organic radical of at least 12 carbon atoms inchain length, the pH of said water being within the range of 5.5 to 8.5.i

3. A non-corrosive industrial process water which comprises a majorportion of water, 10 to 200 parts per million of an alkali metalchromate, calculated as C10 and 0.5 to 10 parts per million of a waterdispersible quaternary ammonium halide which contains one acyclicorganic radical of at least 16 carbon atoms in chain length, the pH ofsaid water being within the range of 5 .5 to 8.5.

4. A non-corrosive industrial process water which comprises a majorportion of water, from 10 to 200 parts per million of an alkali metalchromate, calculated as Cr0 and from 0.5 to 10 parts per million of awater dispersible quaternary ammonium chloride of the formula R1 Cl.-

where R, is. a higher aliphatic group of from 1.6 to 18 carbon atomsinchain length and R R and R are lower aliphatic hydrocarbon groupshaving from 1 to 6 carbon atoms, the pH of said water being within therange of 6.5 to 7.5.

5. The non-corrosive industrial process water of claim 4 where the Waterdispersible quaternary ammonium chromate is octadecyl trimethyl ammoniumchloride.

6. A non-corrosive industrial process water which comprises a majorportion of water, at least 10 parts per million of a water solublehexavalent compound of chromium, calculated as CrO at least 0.5 part permillion of a water dispersible quaternary ammonium salt which containsat least 8 carbon. atoms in, an acyclic chain and at least 0.25 part permillion of an ionizable compound having a cationic heavy metal radicalfrom the group consisting of zinc, cobalt, nickel, mercury and trivalentchromium, the pH of said water being within the range of 5.5 to 8.5.

7. A non-corrosive industrial process water which comprises a majorportion of water, at least 10 parts per million of a water solublehexavalent compound of chromium, calculated as CrO at least 0.5 part permillion of a water dispersible quaternary ammonium salt which has atleast one acyclic organic radical of at least 12 carbon atoms in chainlength, and at least 0.25 part per million of an ionizable compoundhaving a cationic heavy metal radical from the group consisting of zinc,cobalt, nickel, mercury and trivalent chromium, the pH of said waterbeing within the range of 5.5 to 8.5.

8. A non-corrosive industrial process water which comprises a majorportion of water, at least 10 parts per million of an alkali metalchromate, calculated as CrO at least 0.5 part per million of awaterdispersible quaternary ammonium halide which contains one acyclicorganic radical of at least 16 carbon atoms in chain length and from 0.25 to 6 parts per million of an ionizable compound having a cationicheavy metal radical from the group consisting of zinc, cobalt, nickel,mercury and trivalent chromium, the-pH of said water being withinv therange of 5 .5 to 8.5.

9. A non-corrosive industrial process water which comprises a majorportion of water, from 10 to 200 parts per million of an alkali metalchromate, calculated as CrO from 0.5 to 10 parts per million of a waterdispersible quaternary ammonium chloride of the formula Where R is ahigher aliphatic group of from 16 to 18 carbon atoms in chain length andR R and R are lower aliphatic hydrocarbon groups having from 2 to 6carbon atoms, and from 2 to 6 parts per million of an ionizable compoundhaving a cationic heavy metal radical from the group consisting of zinc,cobalt, nickel, mercury andtrii3 valent chromium, the pH of said waterbeing within the range of from 6.5 to 7.5.

10. The non-corrosive industrial process water of claim 9 wherein thewater dispersible quaternary ammonium chloride is octadecyl trimethylammonium chloride and the ionizable compound of the heavy metal has acationic zinc radical.

11. The non-corrosive industrial process water of claim 9 which alsocontains from 0.5 to 2 parts per million of a molecularly dehydratedphosphate, calculated as P 12. The process of protecting metals againstcorros on by contact with aqueous liquids which comprises feeding fromseparate supply sources into an aqueous industrial process water havinga pH within the range of 5.5 to 8.5, an amount of a water solublehexavalent compound of chromium calculated as C suflicient to provide insaid water at least 10 parts per million thereof, and an amount of awater dispersible quaternary ammonium salt sufficient to provide from 20to 60 parts per million thereof in said water, said quaternary ammoniumsalt having at least one acyclic organic radical with at least 8 carbonatoms, contacting the metals of an aqueous process system with saidwater subsequent to said feeding, for a period of time ranging from 7hours to 30 days sutiicient to establish a protective film on saidmetals, and then continuing to treat said metals with said water whilemaintaining feeding of said quaternary salt in amounts sufficient tomaintain said protective film.

13. The process of claim 12 wherein feeding is sufficient to provide insaid water from 10 to 200 parts per million of a water solublehexavalent compound of chromium, and 0.5 to 10 parts per million of awater dispersible quaternary ammonium salt, and wherein the saidquaternary ammonium salt has at least one acyclic organic radical of atleast 12 carbon atoms in chain length.

14. The process of claim 13 wherein the water soluble hexavalentcompound of chromium is an alkali metal chromate and the waterdi'spersible quaternary ammonium salt is a quaternary ammonium halidehaving one acyclic organic radical of at least 16 carbon atoms in chainlength.

15. The process of claim 14 wherein the quaternary ammonium halide hasthe formula:

where R is a higher aliphatic group of from 16 to 18 carbon atoms inchain length and R R and R are lower aliphatic hydrocarbon groups havingfrom 1 to 6 carbon atoms.

16. The process of claim wherein the quaternary ammonium halide isoctadecyl trimethyl ammonium chloride.

17. The process of protecting metals against corrosion by contact withaqueous liquids which comprises feeding from separate supply sourcesinto an aqueous industrial process water having a pH within the range of5.5 to 8.5, an amount of a water soluble hexavalent compound of chromiumcalculated as CrO sufficient to provide in said Water at least 10 partsper million thereof, and an amount of a water dispersible quaternaryammonium salt sulficient to provide from 20 to 60 parts per millionthereof in said water, and also feeding into said Water from a supplysource in an amount sufiicient to provide in said water at least 0.25part per million of an ionizable compound having a cationic heavy metalradical from the group consisting of zinc, cobalt, nickel, mercury andtrivalent chromium, said quaternary ammonium salt having at least oneacyclic organic radical with at least 8 carbon atoms, contacting themetals of an aqueous process system with said water subsequent to saidfeeding for a period of time ranging from 7 hours to 30 days sufiicicntto establish a protective film on said metals, and then continuing totreat said metals with said water while maintaining feeding of saidquaternary salt in amounts sufiicient to maintain said protective film.

18. The process of claim 17 wherein the quaternary ammonium salt has atleast one acyclic organic radical of at least 12 carbon atoms in chainlength.

19. The process of claim 18 wherein the quaternary ammonium salt is aquaternary ammonium halide containing one acyclic organic radical of atleast 16 carbon atoms in chain length, and wherein feeding is sufiicientto provide in said water from 0.25 to 6 parts per million 2 saidionizable compound having a cationic heavy metal radical.

20. The process of claim 19 wherein the quaternary ammonium halide hasthe formula:

in where R is a higher aliphatic group of from 16 to 18 carbon atoms inchain length and R R and R are lower aliphatic hydrocarbon groups havingfrom 1 to 6 carbon atoms, and wherein feeding is sufiicient to providein said water 2 to 6 parts per million of said ionizable com poundhaving a. cationic heavy metal radical, and wherein the pH of said wateris Within the range of from 6.5 to 7.5.

21. The process of claim 20 wherein the quaternary ammonium chloride isoctadecyl trimethyl ammonium chloride and the ionizable compound of aheavy metal has a cationic zinc radical.

22. The process of claim 21 wherein feeding is further maintainedsufiicient to provide in said water from 0.5 to 2 parts per million ofa. molecularly dehydrated phosphate, calculated as P0 References (Iitedin the file of this patent UNlTED STATES PATENTS 2,274,058 Goebel et al.Feb. 24, 1942 2,325,359 Arnold et al July 27, 1943 2,711,391 Kahler June21, 1955 2,738,325 Rydell Mar. 13, 1956 2,793,932 Kahler et al. May 28,1957 2,872,281 Kahler et a1. "Feb. 3, 1959 2,877,085 George et al Mar.10, 1959 2,900,222 Kahler et a1. Aug. 18, 1959 2,947,703 Larsonneur Aug.2, 1960 UNITED STATES PATENT. OFFICE CERTIFICATE OF CORRECTION Patent No3,079,220, February 26,, 1963 David B. Boies et a1.

ppears in the above numbered pet- It is hereby certified that error 51id Letters Patent should read as ent requiring correction and that these corrected below.

Column 12, line 72, for "2" read 1 Signed and sealed this 17th day ofDecember 1963.

Attest:

(SEAL) EDWIN E. REYNOLDS ERNEST w. SWIDER I v Commissioner of PatentsAttesting Officer

12. THE PROCESS OF PROTECTING METALS AGAINST CORROSION BY CONTACT WITHAQUEOUS LIQUIDS WHICH COMPRISES FEEDING FROM SEPARATE SUPPLY SOURCESINTO AN AQUEOUS INDUSTRIAL PROCESS WATER HAVING A PH WITHIN THE RANGE OF5.5 TO 8.5, AN AMOUNT OF A WATER SOLUBLE HEXAVALENT COMPOUND OF CHROMIUMCALCULATED AS CRO4 SUFFICIENT TO PROVIDE IN SAID WATER AT LEAST 10 PARTSPER MILLION THEREOF, AND AN AMOUNT OF A WATER DISPERSIBLE QUATERNARYAMMONIUM SALT SUFFICIENT TO PROVIDE FROM 20 TO 60 PARTS PER MILLIONTHEREOF IN SAID WATER, SAID QUATERNARY AMMONIUM SALT HAVING AT LEAST ONEACYCLIC ORGANIC RADICAL WITH AT LEAST 8 CARBON ATOMS, CONTACTING THEMETALS OF AN AQUEOUS PROCESS SYSTEM WITH SAID WATER SUBSEQUENT TO SAIDFEEDING, FOR A PERIOD OF TIME RANGING FROM 7 HOURS TO 30 DAYS SUFFICIENTTO ESTABLISH A PROTECTIVE FILM ON SAID METALS, AND THEN CONTINUING TOTREAT SAID METALS WITH SAID WATER WHILE MAINTAINING FEEDING OF SAIDQUATERNARY SALT IN AMOUNTS SUFFICIENT TO MAINTAIN SAID PROTECTIVE FILM.